Generator systems that are installed in aircraft may include three separate brushless generators, namely, a permanent magnet generator (PMG), an exciter, and a main generator. The PMG includes permanent magnets on its rotor. When the PMG rotates, AC currents are induced in stator windings of the PMG. These AC currents are typically fed to a regulator or a control device, which in turn outputs a DC current. This DC current next is provided to stator windings of the exciter. As the rotor of the exciter rotates, three phases of AC current are typically induced in the rotor windings. Rectifier circuits that rotate with the rotor of the exciter rectify this three-phase AC current, and the resulting DC currents are provided to the rotor windings of the main generator. Finally, as the rotor of the main generator rotates, three phases of AC current are typically induced in its stator windings, and this three-phase AC output can then be provided to a load such as, for example, electrical aircraft systems.
Because the generators installed in aircraft will often be variable frequency generators that rotate in the speed range of 12,000 rpm to 24,000 rpm, large centrifugal forces are imposed upon the rotors of the generators. Consequently, the rotors should be robust enough to tolerate such forces over long periods of time, and also be precisely balanced to minimize inefficiencies and the risk of failures associated with improper balancing. Designs that strictly define the positioning and allowable tolerances of components within the generator rotors are therefore important, and manufacturing processes for the assembly of components likewise should be performed within rigorously predefined tolerances.
Several aircraft generator components are employed to provide DC current from the rectifier circuits of the exciter to the rotor windings of the main generator. The exciter itself typically provides three phases of AC current that should be independently rectified by respective rectifier circuits and then provided to the rotor windings. In one conventional system, three sets of electrical connections between the rectifier circuits and the rotor windings allow current to pass therebetween. These electrical connections between the rotor windings and the rectifier circuits are provided merely by extending the wire windings from the rotor directly to the rectifier circuits.
This conventional system has certain drawbacks that reduce the overall reliability and balancing of the generators. In particular, because the connections between the rectifier circuits and the rotor of the main generator are provided by wires, the wire connections over time can become weakened or even break due to the repeated application of strong centrifugal forces. Although in certain embodiments the wire extensions may be secured by glue or another fastener to the central shaft of the rotor, the process of securing the wire extensions during manufacturing of the rotor can be laborious and/or imprecise, potentially leading to improperly-balanced rotors. Further, it may be the case that only certain portions of the wire extensions are actually secured, while other portions of the wire extensions remain free to move and bend as the generator rotates. This tends to reduce the reliability of the rotors and can also lead to improper balancing of the rotors.
Thus, there is a need for a high-speed generator with an improved coupling to connect the DC power output from the rectifier circuits of the exciters with the rotor windings of the main generators in order to provide improved balance and/or improved reliability and/or more convenient manufacture of the generator. The present invention fulfills this need and provides one or more of the foregoing advantages.